1. Field of the Inventions
The present inventions relate generally to electronic devices and, more particularly, to the prevention of damage that can occur when users attempt to improperly connect electronic devices to one another.
2. Description of the Related Art
There is a virtually unlimited number of instances where one electronic device is connected to another. Many times, electrical devices will be damaged when they are not connected properly or are connected to a device other that for which connection was intended. This problem is especially acute when the devices are small and when a variety of similar devices are available for essentially the same purpose. One example of such an electronic device is the memory card. Memory cards, which are relatively small devices that are frequently used to store electronic data, have a wide variety of storage applications. A common application is the storage of digitized still or motion images recorded with a digital camera. The memory card may be easily removed from the camera and connected to a personal computer, digital picture frame or printer. Another common application is the storage of sound data, such as musical works that have been downloaded from the internet. Users can, for example, download a musical work with their personal computer, store it on a memory card that is connected to the computer with a suitable adapter or printer card slot, remove the memory card, and then insert the card into a portable player for enjoyment at a remote location. Other applications include laptop computers, palmtop computers, personal digital assistants, and smart cellular telephones and pagers.
Memory cards include a storage medium, such as a flash memory device or a miniature hard disk storage device, that is located within a protective housing. The storage medium is connected to multiple pin sockets, multiple pin contact pads or some other series of multiple electrical contacts that are either located on, or are accessible through, the exterior of the housing. The electronic device used in conjunction with the memory card (or "host device") will include an I/O port with a connector having a corresponding series of pins or other electrical contacts. The pins mate with the sockets or contact pads in the memory card when the memory card is properly inserted into I/O port, thereby electrically connecting the memory card to the host device.
A wide variety of memory cards are available. Digital cameras are typically designed to accept the Compact Flash memory card, of which there are presently two types. The Type I card is 36 mm long, 42 mm wide and 3.3 mm thick, while the Type II card is 36.4 mm long, 42.8 mm wide and 5 mm thick. Digital music recording and playback devices are typically designed to accept either the SmartMedia memory card, which is 45 mm long, 37 mm wide and 0.8 mm thick, or the Multimedia card, which is 32 mm long, 24 mm wide and 1.4 mm thick. Certain digital cameras also accept the SmartMedia card. Some companies have developed their own standard memory card, which can be used in a variety of devices produced by that particular company. The Sony Memory Stick, which is 50 mm long, 21.6 mm wide and 2.8 mm thick, is one example of such a company specific memory card. The pin sockets or contact pads are associated with an edge of the housing that defines the width of the memory card and I/O ports are typically dimensioned to accept particular memory cards. Thus, in the case of a Type I Compact Flash memory card, a corresponding I/O port would have an entrance that is about 42 mm wide and about 3.3 mm high and would also have a connector with a series of pins arranged such that they will mate with the sockets or contact pads when the memory card is inserted.
Given the relatively small size of memory cards and the availability of a wide variety of similarly sized cards, it is not surprising that users make mistakes when attempting to use the cards. For example, users may attempt to insert a memory card into an I/O port sideways in those instances where the memory card, such as a Compact Flash memory card, is wider than it is long. Users will also insert one type of memory card into an I/O port that is designed for another type of memory card. In either event, the typical result is irreversible damage to the connector pins within the digital camera, printer, music player or other host device.
Another common user mistake is the placement of a memory card into its intended I/O port upside down. In those instances where the sockets or contact pads are symmetrical, such as in a Compact Flash memory card, the pins in the I/O port connector will mate with the sockets or contact pads and an electrical connection will be made with the host device despite the fact that the card is upside down. However, because the memory card is upside down, the individual pins will not be connected to the proper sockets or contact pads. In the case of the Compact Flash memory card, outputs from the associated electronic device will drive outputs on the memory card, thereby damaging the card or host device.
One conventional solution to the problem of users inserting memory cards into I/O ports upside down is to mechanically key the memory card and I/O port by including differently sized slots on the sides of the card and correspondingly sized rails on each side of the port. The inventors herein have determined that this solution is less than satisfactory because the keying features are nearly the same. For example, the wrong type of memory card can still be forced into the I/O port in those instances where the card has a side that is narrower than the entrance to the I/O port. Another problem is particular to the Compact Flash memory cards. The inventors herein have determined that Type I Compact Flash memory cards can be forced, either upside down or sideways, into an I/O port that is designed to accept both Type I and Type II Compact Flash memory cards.
Another conventional solution to the problem of improperly inserted memory cards is electronically determine whether the card has made a proper electrical connection with the host device prior to the commencement of card based operations. Compact Flash memory cards, for example, have two symmetrically located internally grounded pin sockets or pin contact pads that are used for card detection purposes and are often referred to as nCD1 and nCD2 contacts. When the Compact Flash memory card is properly inserted into the intended I/O port, the nCD1 and nCD2 contacts will be connected to a pair of card detect lines and to a pair of pullup resistors in the manner illustrated in FIG. 8. The host device (such as a printer) uses a hardware, software or firmware based detection system to determine whether the card detect lines are connected to ground, i.e. whether the logic signals from on the card detect lines are "0." If the logic signals from both card detect lines are "0," then the system determines that the memory card has been properly installed and card based operations may proceed. If one of the logic signals is "1" and the other is "0," then the system determines that the memory card is improperly installed and provides a message to the user (typically on the display of the associated device). Finally, if both of the logic signals are "1," the system determines that the memory card has not been installed.
The inventors herein have determined that the conventional method checking the logic signals associated with the nCD1 and nCD2 contacts in a Compact Flash memory card is susceptible to improvement because the conventional method will not detect when the memory card has been inserted into its intended I/O port upside down. This is because the nCD1 and nCD2 contacts are symmetrically located on the memory card. As such, when the memory card is inserted into the I/O port upside down, both of the card detect lines will be connected to a grounded contact on the memory card (albeit the wrong one) and the firmware or hardware will see logic "0" signals on each of the card detect lines. Card based operations will then be enabled, which can result in damage to the memory card or host device.